A whole laser marking
head (or called laser scanner) consists of two scan mirrors, two
galvanometers (or called galvo-scanner motor) & drive cards, a XY
mount, a scanning lens (f-theta lens), an interface card (or called
D/A card), a set of marking software and a DC power supply. Two
types of scanning optics for CO2 and Nd:YAG lasers are available.

Basics of 2-axis laser scanners

A laser beam is reflected from two scan mirrors in
turn, and directed through a focusing lens. The mirrors are capable
of high speed deflection about a rotation axis, being driven by a
galvo-scanner motor. In most cases the maximum deflection angle of
the mirror is ±12.5° (often ±10° is a safer limit) either side of
the non-deflected incidence angle of 45°.

Note
that, for best performance, the lens will appear to be ‘the wrong
way round’ when compared with a standard meniscus lens used in
conventional focusing of a laser beam.

Some of the design objectives in specification of
2-axis laser scanners are:

Achievement of desired scanned field size

Maximization of scan speeds

Minimizing focused spot sizes

Lowest cost solutions

Some of the limitations to be considered are:

Quality factor Q (Q = M2)
of the laser beam

Scan angle limitations

Loss of power due to beam-clipping

Physical aperture of the scanner head

Field of scan

The laser beam will be scanned over an angle q, equal
to twice the mirror deflection angle. So, the typical scanned field
might be q=±20° in both X and Y directions. (q=±25° would be the
usual maximum scanned field). The field size is then approximately
2Ftanq in both X and Y.

The approximation arises because:

1) it is usually desirable to have a deliberate
distortion characteristic in the scanner lens design so that the
field position is proportional to q, not tanq.

2) scanning in two axes produces a geometrical
distortion which is unrelated to the lens properties.

Example: A TEM00 beam (Q=1) of 13.5mm (1/e2)
diameter, focused by a perfect lens of 100mm focal length, will form
a focused spot of 100mm diameter. (Taking a more realistic value of
Q=1.5, the spot size would be 150mm).

Beam clipping and optical aberrations can lead to
focused spot sizes which are larger than the minimum diffraction
limited value found from the equation above.

Large field sizes demand the use of lenses of long
focal length. In turn, this leads to increased focused spot size
unless the beam diameter, mirror sizes, and lens diameter are all
increased.

Spot sizes are given in the form of an average spot
size over the whole, maximum, field-of-scan. A second figure, the
standard deviation from average spot size, gives a measure of
variation of the spot size to be expected over the field.

Beam clipping

The physical aperture of a laser scanner is often
limited by a circular aperture of the scanner head, of diameter ‘A’
mm, say.

Beam clipping can occur at a circular aperture, even
for a well-centred beam, when the ‘tails’ of the beam energy
distribution is blocked by the metalwork. The percentage power loss
at a circular aperture, for a TEM00 beam (Q=1) is shown
in the following table:

Table: Power Loss

A/D

0.8

1

1.2

1.4

1.6

1.8

2

Loss %

27.8

13.5

5.6

1.98

0.6

0.15

0.03

The table indicates that, where the physical aperture
of the scanner is limited to A mm diameter, the laser beam diameter
D (1/e2) must be selected by a compromise between reduced
spot size and power loss due to beam clipping. A value of D = A/1.4
would probably be acceptable for most laser scanner systems. Power
loss due to beam clipping increases for de-centred beams.

Mirror design

Mirror (1) (or called Scan Mirror X)

The width of mirror (1) is determined by the beam
diameter. It is easier to discuss this in terms of a ‘full beam
diameter’ DF, where the definition of full diameter is,
to some extent, arbitrary.

For example, a system designer might define DF
as the measured diameter of a beam print in perspex [plexiglass].
Alternatively, DF may be the measured 99% power points,
or perhaps a value chosen in the range 1.4D to 1.6D.

The mirror width W1 is slightly larger than the
selected value of DF, sufficient to allow for minor
misalignment. The length of mirror (1) is determined by the maximum
angle of incidence imax on the mirror. Let a= (90°-imax).
Then the mirror length is L1, where L1 = W1/sina. The large shape
‘chamfers’ on scanner mirrors are determined by the separation, S1,
between mirrors (1) and (2); the scan angles, and the need that the
mirrors should not collide during scanning.

Mirror (2) (or called Scan Mirror Y)

The width of mirror (2), W2, should be identical to
the length of mirror (1). The length, L2, of mirror (2) is found
from projection of the beam onto the second mirror at a distance of
S1, and at maximum scan angle q. These mirrors are built and coated
specifically for use with CO2 or YAG lasers. They have a very
high laser damage threshold, measured at 1000W/mm of 1/e2
beam diameter (D).

F-theta characteristic

Lenses described as being ‘F-theta’, or ‘Fq’, type
are designed so as to produce an off-axis spot at a location
proportional to the scan angle. In turn, this may be directly
proportional to a voltage applied to the galvo scanner motor. (A
lens with zero distortion would form a spot at a field location of
Ftanq). No 2-axis galvo scanner can have a true F-theta
characteristic, due to distortion from use of two mirrors.
Single-element lenses are designed to be the best compromise between
smallest spot size and F-theta characteristic. Errors in F-theta
characteristic are usually 2% - 3% for these single element lenses.
Multi-element lenses allow design freedom enabling a closer approach
to F-theta performance. Fq errors <0.36% are typical for this range,
with only the 75mm FL type having a slightly greater value.

Lens design

All scanning lens designs are based on factors
described above. For typical small scanner systems, limited to
perhaps 10mm or 15mm full beam diameter, lenses of 48mm diameter
have been found to be suitable. For 15mm beams, this lens size is
only possible by minimizing the distances S1 and M2L. Each class of
lens is designed for use with a specific range of beam diameters,
and, more importantly, for a specific set
of values S1 and M2L.

In each case the lens is designed to provide the best
compromise performance for flat field, spot size and F-theta
characteristic for the specified beam diameter and mirror locations,
while avoiding beam-clipping at the lens mount.

For certain (longer focal length, single-element)
lenses it is possible to obtain an improvement in performance by
increasing the distance M2L. This necessitates the design/use of
lenses of larger diameter (to avoid beam clipping).

F-theta
lens STY-532-110-160 is used in above specifications. LSSL,
LSHL & LSGT marking heads are digital heads and their port is
XY2-100.

Remark:

The marking
field of our standard marking head
is 105x105mm (CO2 laser) or 110x110mm (Nd:YAG laser). Other mark
fields are available upon request. In fact,
the marking field depends on the f-theta lens. Thus you may
prepare a few f-theta lenses with different marking fields for
your various applications.

The focused beam
diameter is theoretical calculation for reference only and
actual focused beam diameter depends on beam expander, f-theta
lens and laser.

In LSCT series
marking heads, the galvos and drivers are made in the USA. In
LSSL series marking heads, the galvos, drivers and scan mirrors
are made in Germany.

All above
analogue marking heads can be converted into digital marking
heads via a D/A convertor as follows:

In order to meet the
experienced customers’ requirement on cost, we also supply BASIC
laser marking head which just includes the basic parts such as
galvanometers and drivers, scan mirrors, DC power supply and all
mechanical parts. BASIC marking heads are integrated and aligned for
use. The model numbers will be LSCT-xxxx-yy-AAAA-BASIC or
LSST-xxxx-yy-AAAA-BASIC.

The
standard scan head for laser labeling
The LLSL-BC 10's full 10-mm aperture is ideal for use with fiber
lasers. Its ultra-compact housing facilitates very straightforward
integration into production lines. And it offers impressive
dynamics, e.g. 800 cps with good writing quality.

LLSL-BC is available for four different wavelengths (355 nm, 532 nm,
1064 nm or 10600 nm) and is combinable with a variety of objectives.
Control is via the digital XY2-100 protocol.

Specifications

Dynamic

Aperture
[mm]

10

Tracking error [ms]

0.14

Typical speed

Marking speed [m/s]

2.5

Positioning speed [m/s]

12

Good quality writing Speed [cps]

800

High quality writing Speed [cps]

570

Step response time

1% of full scale [ms]

0.35

10% of full scale [ms]

1.0

Precision &
Stability

Repeatability (RMS)
[urad]

<2.0

Positioning
resolution [Bit]

16

Non-linearity

<3.5mrad/44

Temperature drift

offset [urad/K]

<30

Gain [ppm/K]

<160

Long term drift (8 hrs)

Offset [urad]

<100

Gain [ppm]

<250

Further
Specifications

Optical performance

Typical scan angle [rad]

±0.35

Gain error [mrad]

<5

Zero offset [mrad]

<5

Power requirement

±15 VDC, 3A each

Interface

XY2-100

Operating Temperature (°C)

25 ± 10

LSSL

Portable size, Fast speed, High accuracy

LSSL series
laser marking head is an ultra-compact one which delivers excellent
dynamics and superior product quality in a minimum-size package. The
solid performance of the marking heads is made possible by the new,
miniaturized servo amplifiers and industry-proven OSSL series
galvanometer optical scanners. Aperture of 7, 10 and 14mm are available.

Sealed against water and dust, the LSSL robust and
exceptionally compact housing facilitates straightforward integration
into production environments-even confined, difficult to-access
locations. A wide variety of objectives can be used with these scan
heads.

Versions with analog or digital interfaces are available.
The digital version can be simply controlled via a PCI interface board
or PC-independent standalone board. LSSL scan heads are ideally suited
for solutions requiring very high marking speeds and integration in
confined spaces. Applications include coding in the packaging industry
or the marking of electronic components – areas traditionally served by
inkjet systems.

Optics

We precisely optimize and tune all optical components to
one another to ensure maximum focus quality and stable process
parameters. Optical components offered by us include exceptionally
compact objectives, as well as objective adapters for standard
objectives. Optics for various wavelengths, power densities, focal
lengths and image fields are available.

Control

LSSL marking heads are equipped with either an analog or
a digital standard interface accessible via a 25-pin D-SUB connector.
They are easily controlled via PC interface board or the PC-independent
standalone board from us.

Quality

The high quality is the result of years of experience in
the development and manufacture of galvanometer optical scanners and
scan systems. In addition, every scan system must first pass the quality
check burn-in test before it is released for shipment to the customer.

STRM-Atom Series is a totally digital 2D galvanometer system. Embedded
control system guaranteed the servo loop operation. It is compact,
stable and cost-efficiency. It is the basic version of STRM series
scanheads. Mirrors of general wavelength is available, like 1064nm,
532nm 355nm, 10.6um.Suitable
for laser marking, microscope, drilling, trimming and cutting etc.

Specifications

(All
angles are in optical degrees)

Aperture

10mm

Beam
displacement

13mm

Tracking error
time

220us

Offset drift

75urad/K

Gain drift

200ppm/K

Step response
time

1% of full
scale

0.3ms

10% of full
scale

0.8ms

Marking speed
(1)

2m/s

Positioning
speed

12m/s

Writting speed
(2)

Good quality

500cps

High quality

450cps

Repeatability

< 22urad

Drift over 8
hours (After 30min warm-up)

< 0.3mrad

Typical scan
angle

40 degrees

Interface (3)

XY2-100
Enhanced

Operating
temperature

25°C±10°

Power
requirements

±15V DC, 150W

Driver mode

Digital

Resolution

16Bit

Max laser
power (4)

100W

(1)with
F-Theta objective, f=160mm

(2)single-stroke characters of 1mm height

(3)XY2-100
Enhanced with status feedback

(4)The mirror
of 1064nm can stand max laser power

STRM-Q 10/12/14/20/30

STRM-QUANTUM series is totally digital
2D galvanometer system. System operate based on the embedded
platform. It is compact, stable and high quality. More fast and
accuracy. The offset drift and gain drift are very low. Mirrors of
typical laser wavelength is available and optimized for inertial and
stiffness. Suitable for high end application like ITO scratching,
laser micro processing etc. (Added water and air cooling function to
20 and 30 to improve the stability of the system.)

Specifications

(All
angles are in optical degrees)

STRM-Q 10

STRM-Q 12

STRM-Q 14

Aperture

10mm

12mm

14mm

Beam
displacement

13mm

14.5mm

18.1mm

Tracking
error time

130us

160us

160us

Offset
drift

30urad/K

30urad/K

30urad/K

Gain drift

50ppm/K

50ppm/K

50ppm/K

Step
response time

1% of full
scale

0.3ms

0.3ms

0.5ms

10% of
full scale

0.8ms

0.8ms

1ms

Marking
speed (1)

2.5m/s

2m/s

2m/s

Positioning speed

15m/s

11m/s

8m/s

Writting
speed (2)

Good quality

800cps

660cps

660cps

High quality

500cps

410cps

410cps

Repeatability

< 15urad

< 15urad

< 15urad

Drift over
8 hours (After 30min warm-up)

< 0.1mrad

< 0.1mrad

< 0.1mrad

Typical
scan angle

40 degrees

40 degrees

40 degrees

Interface
(3)

XY2-100
Enhanced

XY2-100
Enhanced

XY2-100
Enhanced

Operating
temperature

25°C±10°

25°C±10°

25°C±10°

Power
requirements

±15V DC,
150W

±15V DC,
150W

±15V DC,
150W

Driver
mode

Digital

Digital

Digital

Resolution

16Bit

16Bit

16Bit

Max laser
power (4)

100W

100W

100W

(1)with
F-Theta objective, f=160mm

(2)single-stroke characters of 1mm height

(3)XY2-100
Enhanced with status feedback

(4)The
mirror of 1064nm can stand max laser power

STRM-Q20

STRM-Q30

Aperture

20mm

30mm

Beam displacement

26.5mm

36.5mm

Tracking error time

360us

550us

Offset drift

30urad/K

30urad/K

Gain drift

50ppm/K

50ppm/K

Marking speed

1m/s

0.7m/s

Positioning speed

6m/s

3m/s

Writing speed

Good quality (1)

320cps

220cps

High quality (2)

210cps

150cps

Repeatability

<15urad

< 15urad

Drift over 8 hours

< 0.1mrad

< 0.1mrad

(After 30min warm-up) Typical scan angle

40 degrees

40 degrees

Interface

XY2-100 Enhanced

XY2-100 Enhanced

Operating temperature

25°±10°

25°±10°

Power requirements

±15V DC, 150W

±15V DC, 150W

Driver mode

Digital

Digital

Resolution

16Bit

16Bit

Max laser power (3)

1000W

5000W

(1) with F-Theta objective, f=160mm

(2) single-stroke characters of 1mm height

(3) The mirror of 1064nm can stand max laser power in
air cooling

LSGT Series Digital Marking Heads

LSGT digital marking heads are suitable for laser marking
systems, especially in fiber laser marking and CO2 flying
marking applications. They have a good cost performance but the pricing
is attractive.

The high quality of our products is the result of the
combination of the digital servo driver technology and the reliable
manufacturing of the micro motor. All elements of the systems are
manufactured with high standard. The digital servo can efficiently
reduce the electromagnetic interference around the space. We make the
products suitable for long-term and continuous use.